Design and Analysis of Doppler Radar-Based Vehicle Speed Detection

Home , Doppler radar

INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 5, ISSUE 06, JUNE 2016 ISSN 2277-8616 Design And Analysis Of Doppler Radar-Based Vehicle Speed Detection

Su Myat Paing, Su Su Yi Mon, Hla Myo Tun

Abstract: The most unwanted thing to happen to a road user is road accident. Most of the fatal accidents occur due to over speeding. Faster vehicles are more prone to accident than the slower one. Among the various methods for detecting speed of the vehicle, object detection systems based on Radar have been replaced for about a century for various purposes like detection of aircrafts, spacecraft, ships, navigation, reading weather formations and terrain mapping. The essential feature in adaptive vehicle activated sign systems is the accurate measurement of a vehicle’s velocity. The velocities of the vehicles are acquired from a continuous wave Doppler radar. A very low amount of power is consumed in this system and only batteries can use to operate. The system works on the principle of Doppler Effect by detecting the Doppler shift in microwaves reflected from a moving object. Since, the output of the sensor is sinusoidal wave with very small amplitude and needs to be amplified with the help of the amplifier before further processing. The purpose to calculate and display the speed on LCD is performed by the microcontroller.

Keywords: CW Doppler Radar, Doppler Effect, Doppler Shift, Microcontroller, Amplifier. ————————————————————

I. INTRODUCTION The overall system configuration is shown in Figure 2. Radar stands for radio detection and ranging. It operates by There are two main sections in this system: (1) an radiating electromagnetic waves and detecting the echo amplification circuit, and (2) a frequency counter and speed returned from the target. Although radar cannot reorganize display. The Doppler radar transmits the frequency of the collar of the object and resolve the detailed features of 10.525GHz to the vehicle. It reflects back some portion of the target like the human eye, it can see through darkness, the transmitted signal with a shift in the frequency. Since, fog and rain, and over a much longer range. This system the output voltage of the sensor is in small dc value. So, it uses HB series of microwave motion sensor module are X- needs to amplify with the help of the amplifier circuit. The Band Mono-static DRO Doppler transceiver front-end output of the amplifier is fed to the microcontroller. The module(HB100). These modules are designed for microcontroller performs the tasks of calculation of movement detection, like intruder alarms, occupancy frequency, calculation of speed and displays them on the modules and other innovative ideas. The module can detect LCD. the distance within 20m and its transmitted frequency is 10.525GHz. It consists of Dielectric Resonator Oscillator III. DESIGN PROCEDURE (DRO), microwave mixer and path antenna. The oscillator is used to produce a sinusoidal wave of frequency (1) Amplification Circuit 10.525GHz, patch antenna connected to the oscillator 3The output of the sensor is in the audio frequency range radiates the wave towards the target and the reflected wave and small dc value. So, an audio amplifier with low pass is received by another set of patch antenna. The mixer active filter is desired for the design to meet this mixes these two signals to generate a sinusoidal wave with requirement. The complete diagram of the amplifier circuit frequency equal to the difference between the two signals. used is shown in Figure 3. LM324 Quad op-amp is the Figure 1 shows the internal structure of HB100. amplifier IC used for this purpose as the output gets nearly 4.5V which is enough to drive the microcontroller. +5V GND Oscillator

Mixer Tx Rx Antenna Antenna

GND IF

Figure 1: Internal structure of HB100

II. SYSTEM DESCRIPTION

+5V DC SUPPLY

DOPPLER MICROCONTROLLER Figure 3: Circuit Diagram of the Amplifier using LM358N RADAR AMPLIFIER (PIC16F887) (HB100)

DISPLAY SPEED (LM016L)

Design Calculation of Amplifier Circuit to drive the Microcontroller To use LM324 op-amp as driver, it is selected 5V as Vcc. For cascaded stages, Vbias for each stage must be 2.5V.

R 2 Vbias  .Vcc R1  R 2 R 2.5V  2 .5V R1  R 2 R 1 2  R1  R 2 2 Therefor , R  R 100k is selected. Figure 4: Output Waveform of the amplifier using LM358N 1 2 For minimum error due to inupt bias current, it must be reduced to nearly 0.01mA.

Vbias Ibias  R3 2.5V R   250k 3 0.01mA

Therefore, standard value 330k is selected for R3.

For First Stage (Amplification)

Since the output of the sensor is a small dc value, it must Figure 5: Circuit Diagram of the Amplifier using LM324 be amplified at least 100 times to drive the microcontroller.

Assume Av1 100 For non - inverting amplificat ion,

R f1 Av1 1 Rin1

From the data sheet of LM324, Rin1=10kΩ is selected to achieve output voltage about 5V.

R 100  1 f1 10k

Rf1  99 x 10k  990k  1M

Figure 6: Output Waveform of the amplifier using LM324  Rf1  Rf2  1M is selected for both stages.

For AC coupling amplificat ion, Cin  4.7μF is To minimize the effect of the noise, the amplification is achieved in two stages. The first stage is configured as convenient with Rin  10k. non-inverting amplifier. Since the output of the sensor is a Cin1  Cin2  4.7μF is selected for both stages. small dc value (0.01 to 0.2Vdc), AC coupling of the output is necessary. The output of the first stage is a sinusoidal signal with a small dc offset. The dc component at the For Second Stage (low - pass filter) output is filtered by the capacitor at the output terminal. The 1 second stage is configured as inverting amplifier. The 2.2nF f  capacitor in the feedback path of the amplifier makes this c 2πR C configuration an active low pass filter. The high frequency in2 in2 1 noises are filtered and the accuracy of the system is 4Hz  improved. The two stages are cascaded to achieve the 2πRin2(4.7μF) overall gain of the amplifier. The second stage acts as a R  8.4k comparator and the output produced is a digital waveform in2 that can be sensed by the digital pin of a microcontroller. Therefore, standard value 8.2k is selected for Rin2.

(2) Frequency Counter and Speed Display Relation Between Frequency and Speed

f  fr  fo...... Eq : (1) c λ  ...... Eq : (2) fo 2v f  ...... Eq : (3) λ

where; f  Doppler shift

f r  received frequency

f o  transmitted frequency λ  wavelength of transmitted wave c  speed of light v  speed of the vehicle

For Δf  2.5kHz, c 3x108 ms-1 λ    0.0285m 9 fo 10.525x10 cycles/s 2v Figure 6: Pulse Generator Properties window (adding the Δf  λ frequency with 2.5kHz) 2v 2.5kcycles /s  0.0285m v128250mph  128.25kmph

Figure 7: Simulation of the frequency counter after running

Frequency of the signal is the factor representing the speed of the moving object. So, the frequency of the incoming pulse from the amplifier is measured by connecting the Figure 8: Simulation for the speed display output of the amplifier to the timer1 clock input pin of PIC16F887. The corresponding pin in PIC16F887 is pin 15. The speed is calculated by writing the equation of the When used with an internal clock source, the module is a relation between frequency and speed in the existing timer. When used with an external clock source, the module program. can be used as either a timer or counter. In this paper, it is operated as an external clock source. When counting, Start Timer1 is incremented on the rising edge of the external Initialize I/O ports clock input T1CKI. In addition, the Counter mode clock can be synchronized to the microcontroller system clock or run Configure LCD connections asynchronously. In Counter mode, a falling edge must be registered by the counter prior to the first incrementing Extract the digits rising edge after one or more of the following conditions: Set up TMR1  Timer1 is enabled after POR or BOR Reset  A write to TMR1H or TMR1L Set up cnt  T1CKI is high when Timer1 is disabled and when Delay 1 second Timer1 is reenabled T1CKI is low. Read the low byte and high byte of TMR1 The frequency of the input signal can be obtained from Display the counted value and the clock of the counter. A number of frequency & speed on LCD such measurements can be taken and averaged for better Figure 9: Flow Chart for Frequency Counter and Speed accuracy. Display

IV. CONCLUSION In this paper, a low cost and efficient embedded vehicular speed detecting system is presented. The work aimed at implementing the better results by comparing the existing methods such as FFT, DSP and LASAR based techniques. The output was more accurate with no other moving objects in the surrounding. In reality, the radar will not measure the actual velocity when the vehicle is not travelling directly towards the radar and slightly inclined at an angle.

ACKNOWLEDGEMENT The author would like to thanks her supervisor Dr. Su Su Yi Mon, Associate Professor, Department of Electronic Engineering, Mandalay Technological University, for accomplished guidance, helpful suggestions, and continuous supervision. The author is grateful to Dr. Hla Myo Tun, Associate Professor and Head, and all teachers from Department of Electronic Engineering, Mandalay Technological University, for sharing technical knowledge and supporting.

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